Technical Field

The present invention relates to a gearbox.

Background Art

Various types of gearboxes are known, which differ both in shape and size depending on the field of application.

In particular, gearboxes with gears have a very wide range of applications, are simpler and lighter and cost less than hydraulic and electric gearboxes; moreover, they have a higher efficiency because in them the transmission of energy takes place without this changing form.

Gearboxes with gears are based on sets of toothed rims coupled together in sequence to form one or more stages of reduction to reduce the motion transmitted, through a main motor, from an input transmission shaft to an output transmission shaft.

This way, the mechanical characteristics of the main motor (torque and speed) can be adapted to those of a load connected to the output transmission shaft. In fact, motors, in particular electric motors, can generate speeds much higher than those required by the loads, while the output torques are limited.

Generally, the use of a gearbox reduces the speed and increases the torque transmitted by the motor, but greatly increases the size of the motor assembly and makes its use disadvantageous for many industrial applications increasingly aimed at building integrated and small size systems.

To avoid this drawback, the use is known of planetary gearboxes which allow obtaining high reduction ratios with small-size spaces.

However, known planetary gearboxes have a number of drawbacks tied to the lack of a braking mechanism.

In fact, many industrial applications require a braking assembly to stop motion transmission between the input transmission shaft and the output transmission shaft.

More specifically, the braking assembly is used by a variety of industrial applications to prevent the motion from being transmitted in the opposite direction from the output to the input; e.g., an elevator winch must have a braking assembly to keep the load at the desired height and prevent it from falling to the ground after the motor has stopped.

For this reason, a braking assembly must be added to the motor and gearbox. Generally speaking, the braking assembly in turn comprises a motor, e.g. a hydraulic or an electric motor, which considerably increases the space required by the motor-gearbox assembly and invalidates the space reduction obtained through the use of the planetary gearbox.

Furthermore, a braking assembly increases the production cost of the motor- gearbox-brake assembly with consequent increase in the retail price, with the risk of making the products less appealing to customers.

Description of the Invention

The main aim of the present invention is to provide a gearbox which allows reducing the motion transmitted between the input shaft and the output shaft and at the same time comprises a braking assembly to block the transmission of motion between the output shaft and the input shaft.

Another object of the present invention is to provide a gearbox which allows integrating the braking assembly inside it without significantly increasing the size of the gearbox itself.

Another object of the present invention is to provide a gearbox which allows overcoming the aforementioned drawbacks of the prior art within the scope of a simple, rational, easy, efficient to use and cost-effective solution.

The aforementioned objects are achieved by the present gearbox according to claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more evident from the description of a preferred, but not exclusive embodiment of a gearbox, illustrated by way of an indicative, but non-limiting example, in the attached drawings in which:

Figure 1 is an axonometric view of the gearbox according to the invention; Figure 2 is a sectional view of the gearbox according to the invention;

Figure 3 is an axonometric view, in partial transparency, of the gearbox according to the invention; Figure 4 is an exploded view of some elements of the gearbox according to the invention.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally indicates a gearbox.

The gearbox 1 comprises:

at least one base frame 2;

at least one planetary gearbox assembly 3 mounted on the base frame 2 and adapted to transmit the motion generated by at least one drive shaft 13 to motion user means, the planetary gearbox assembly 3 reducing the motion transmitted by the drive shaft 13 to the user means.

The base frame 2, for example, is a rigid substantially U-shaped structure comprising two extremes substantially opposite one another and adapted to support a motor 4 and an output shaft 5 respectively which are associated with the planetary gearbox assembly 3.

The planetary gearbox assembly 3 comprises a side wall 6 and a circular base 7 associated with the side wall 6 to form a container element 8 with a substantially cylindrical shape and defining a circular opening 9 substantially opposite the circular base 7.

Furthermore, the planetary gearbox assembly 3 comprises a closing flange 10 which is associated with the circular opening 9 and is adapted to operate in conjunction with the container element 8 to form a substantially closed cylindrical structure.

More specifically, the circular base 7 of the container element 8 is associated with the motor 4, while the closing flange 10 is associated with the output shaft 5.

This way, the planetary gearbox assembly 3 is suspended interposed between the extremes of the base frame 2 as shown in Figure 1.

Furthermore, the container element 8 is drilled at the center of the circular base 7 to make a circular cavity 11 for fitting the drive shaft 13.

In fact, the drive shaft 13 is set in motion by the motor 4, protrudes from it and passes through the circular cavity 11 to transmit motion to the planetary gearbox assembly 3.

More specifically, the drive shaft 13 and the output shaft 5 are centered along the same rotation axis A and keep the planetary gearbox assembly 3 suspended substantially horizontally between the two extremes of the base frame 2.

Within the scope of the following treatise, the adjective "horizontal" refers to the conditions of use of the gearbox 1 shown in Figure 1 in which the rotation axis A is interposed between the extremes of the base frame 2 substantially parallel to the ground and passes through the center of the circular cavity 11 of the planetary gearbox assembly 3; obviously alternative embodiments of the invention cannot be ruled out wherein the gearbox 1 is oriented differently in space, e.g., with the rotation axis A arranged vertically or obliquely.

The drive shaft 13 is rotating around the rotation axis A to transmit the motion generated by the motor 4 to the planetary gearbox assembly 3.

The gearbox 1 also comprises at least one worm gearbox assembly 12 interposed between the drive shaft 13 and the planetary gearbox assembly 3. In this regard, the gearbox 1 comprises at least one motion deflection assembly 14 from the drive shaft 13 to at least one transmission shaft 15 which is connected to the worm gearbox assembly 12.

The motion deflection assembly 14 comprises at least one bevel gear pair 16 for the transmission of motion from the drive shaft 13 to the transmission shaft 15, the transmission shaft 15 being substantially transverse to the drive shaft 13. The bevel gear pair 16 comprises a sun gear 17 of the bevel type with straight teeth and associated with the drive shaft 13 and an auxiliary gear 18, this too of the bevel type with straight teeth, associated with the transmission shaft 15. More specifically, the sun gear 17, the auxiliary gear 18, and the transmission shaft 15 are arranged inside the container element 8.

Advantageously, the motion deflection assembly 14 comprises a single sun gear 17 and three bevel gears 18, each of which is associated with a corresponding transmission shaft 15.

Furthermore, the teeth of the sun gear 17 are inclined by an angle of approx. 30°, while the teeth of the auxiliary gears 18 are inclined by an angle of approx. 60° and the transmission shafts 15 are arranged substantially orthogonal to the drive shaft 13 and rotating around a respective transmission axis B respectively. Alternative embodiments cannot however be ruled out wherein the teeth of the sun gear 17 and/or the teeth of the bevel gears 18 are inclined by a different angle respectively, e.g., wherein both the teeth of the sun gear 17 and the teeth of the auxiliary gears 18 are inclined by an angle of approximately 45°.

In the specific embodiment shown in the figures, the sun gear 17 is provided with a number of teeth amounting to thirty- two, while each auxiliary gear 18 coupled to the sun gear 17 is provided with a number of teeth amounting to sixteen.

This way, the motion deflection assembly 14 is also a motion multiplication assembly with a transmission ratio of 0.5 for each sun gear 17 - auxiliary gear 18 pair.

Alternative embodiments cannot however be ruled out wherein the number of teeth of the sun gear 17 and the auxiliary gear 18 are different.

The worm gearbox assembly 12 comprises at least one worm screw 19 associated with the transmission shaft 15.

Conveniently, the worm gearbox assembly 12 comprises three worm screws 19, each of which is associated with the corresponding transmission shaft 15 in the proximity of the relative auxiliary gear 18.

This way, each worm screw 19 rotates at the same angular speed as the corresponding auxiliary gear 18.

The worm gearbox assembly 12 also comprises a deflection gear 20 for deflecting motion from the transmission shaft 15 to at least one actuating shaft 21 associated with the planetary gearbox assembly 3.

Advantageously, the worm gearbox assembly 12 comprises three deflection gears 20, each of which is associated with a corresponding actuating shaft 21. Furthermore, the planetary gearbox assembly 3 comprises:

at least one planet gear toothed wheel 22 associated with the actuating shaft

21;

- at least one planet gear carrier structure 23 adapted to carry the actuating shaft 21; and

at least one inner toothed rim 24 coupled to the planet gear toothed wheel 22.

Conveniently, the planetary gearbox assembly 3 comprises three planet gear toothed wheels 22 associated with an actuating shaft 21 respectively in the proximity of the corresponding deflection gear 20.

Usefully, the planet gear carrier structure 23 is defined by the union of the container element 8 and the closing flange 10.

More specifically, the closing flange 10 can be attached to the container element 8 to close the circular opening 9 and, at the same time, to support the actuating shafts 21 between the closing flange 10 and the container element 8.

The planet gear carrier structure 23 comprises a pair of supporting seats 32, of which one supporting seat 32 is obtained on the closing flange 10, while the other supporting seat 32 is obtained on the circular base 7 of the container element 8 in the proximity of the circular cavity 11.

More specifically, the supporting seats 32 are arranged substantially facing and opposite each other when the closing flange 10 is attached onto the container element 8.

Advantageously, the planet gear carrier structure 23 comprises two supporting seats 32 for each actuating shaft 21.

This way, the actuating shafts 21 are arranged inside the planet gear carrier structure 23 and interlocked between the circular base 7 and the closing flange 10 through the corresponding pair of supporting seats 32.

Furthermore, the actuating shafts 21 are rotating around a corresponding actuating axis C and are arranged substantially parallel to the rotation axis A. The planet gear carrier structure 23 also comprises a groove 25 obtained in the proximity of the circular opening 9 and hollowed along the entire length of the circumference of the side wall 6 to define an interlocking portion for the inner toothed rim 24.

The groove 25 is drilled at the actuating shafts 21 to arrange the planet gear toothed wheels 22 partially outside the planet gear carrier structure 23 to engage the inner toothed rim 24.

In fact, the inner toothed rim 24 is arranged around the groove 25 and partially fits over the planet gear carrier structure 23 to engage the planet gear toothed wheels 22.

The planetary gearbox assembly 3 comprises at least one supporting element 26 associated with the planet gear carrier structure 23, the transmission shaft 15 being associated with the planet gear carrier structure 23 and with the supporting element 26.

The supporting element 26 is a body having a section with substantially triangular shape and comprises three flat sides 27 of substantially rectangular shape and contiguous to each other.

Furthermore, the supporting element 26 is drilled to make a transversal channel 28 on each flat side 27 of the supporting element 26 and a longitudinal channel

29 at the center of the triangular section of the supporting element 26.

Advantageously, each transversal channel 28 is obtained substantially orthogonal to the longitudinal channel 29 and forms an angle of 120° with respect to the other transversal channels 28.

In this regard, the planet gear carrier structure 23 is hollowed to create a side hole 30 on the side wall 6 of the container element 8 for each transversal channel 28 made on the supporting element 26.

In fact, the supporting element 26 is associated with the circular base 7 of the container element 8 inside the planet gear carrier structure 23 with the longitudinal channel 29 facing the circular cavity 11 and the transversal channels 28 facing the corresponding side holes 30.

This way, each transversal channel 28 - side hole 30 pair defines a support which permits arranging a transmission shaft 15 interposed between the container element 8 and the supporting element 26 substantially perpendicular with respect to the rotation axis A.

Furthermore, the drive shaft 13 passes through the circular cavity 11 to support the sun gear 17 in the proximity of the mouth of the longitudinal channel 29 between the supporting element 26 and the circular base 7.

The planet gear carrier structure 23, in collaboration with the supporting element 26, allows arranging, as previously described, the motion transmission shafts 13, 15, 21 and the corresponding toothed wheels and gears.

More specifically, the sun gear 17 in collaboration with the planet gear toothed wheels 22 and with the inner toothed rim 24, define a planetary mechanism for the reduction of motion.

Such planetary mechanism is enhanced by the worm screws 19 interposed substantially between the sun gear 17 and the planet gear toothed wheels 22. Each worm screw 19 is coupled to the deflection gear 20, the worm screw 19 being driving and the deflection gear 20 being driven.

The worm screw 19 engages the deflection gear 20 to transmit motion from the transmission shaft 15 to the actuating shaft 21 with a reduction ratio of about twenty.

Alternative embodiments cannot however be ruled out wherein the worm screw

19 and/or the deflection gear 20 are different in order to obtain the transmission of motion with a different reduction ratio, e.g., wherein the worm screw 19 is provided with a number of principles amounting to six and the deflection gear

20 is provided with a number of teeth amounting to forty in order to obtain a reduction ratio of twenty to three.

Advantageously, the reduction ratio of the worm screw 19 and the deflection gear 20 allows the transmission of motion only from the transmission shafts 15 to the actuating shafts 21 while it prevents the transmission of motion from the actuating shafts 21 to the transmission shafts 15.

This way, the worm gearbox assembly 12 is also a braking assembly integrated inside the planetary gearbox assembly 3.

The transmission of motion from the actuating shafts 21 to the user means is by means of the inner toothed rim 24.

In the particular embodiment shown in the illustrations, in fact the planet gear carrier structure 23 is fixed and the user means are associated with the inner toothed rim 24.

More specifically, the planet gear carrier structure 23 is rigidly fixed to the motor 4, which in turn is fixed to the base frame 2.

In this case, the motor 4 rotates the drive shaft 13, which transmits motion to the gears and to the motion transmission shafts 13, 15, 21 arranged inside the planet gear carrier structure 23.

In fact, the drive shaft 13 transmits motion to the transmission shafts 15 through the motion deflection assembly 14.

The transmission shaft 15 transmits motion to the actuating shaft 21 through the worm gearbox assembly 12.

The actuating shaft 21 transmits motion to the planet gear toothed wheel 22 which engages the inner toothed rim 24.

The inner toothed rim 24 is free to rotate to transmit motion to the user means. In the particular embodiment shown in the illustrations, the user means consist of a cylindrical drum 31 which is arranged around the planetary gearbox assembly 3.

The cylindrical drum 31 is associated with the inner toothed rim 24 as a continuation of the body of the inner toothed rim 24 itself.

This way, the gearbox 1 can be used as a winch, e.g., to wind a rope around the cylindrical drum 31.

Conveniently, the planet gear toothed wheel 22 is provided with a number of teeth amounting to twenty- three and the inner toothed rim 24 is provided with a number of teeth amounting to seventy-five.

This way, the motion transmitted by the motor 4 to the cylindrical drum 31 is reduced with a reduction ratio of 130.43.

Alternative embodiments cannot however be ruled out wherein the planet gear toothed wheel 22 and/or the inner toothed rim 24 are provided with a different number of teeth to obtain a different reduction ratio.

Given the nature of planetary mechanisms, by means of a number of structural modifications, the transmission of motion from the actuating shafts 21 to the user means can occur through the planet gear carrier structure 23.

It is easy to understand that alternative embodiments of the invention are in fact possible, wherein the inner toothed rim 24 is fixed and the planet gear carrier structure 23 is moveable, the user means being associated with the planet gear carrier structure 23.

In this case, the inner toothed rim 24 is fixed to the base frame 2, while the planet gear carrier structure 23 rotates inside the inner toothed rim 24.

More specifically, each planet gear toothed wheel 22 rotates on itself around the actuating axis C to engage with the inner toothed rim 24. This way, since the inner toothed rim 24 is fixed, each planet gear toothed wheel 22 rolls along the inner circumference of the inner toothed rim 24 and rotates the planet gear carrier structure 23 around the rotation axis A.

The output shaft 5 is then made to rotate by the planet gear carrier structure 23 to transmit motion to the user means.

In both cases described, the motion is generated by the motor 4, is transmitted through the motion deflection assembly 14 from the drive shaft 13 to the transmission shafts 15, is reduced through the worm gearbox assembly 12 from the transmission shafts 15 to the actuating shafts 21 and is transmitted through the coupling between the planet gear toothed wheels 22 and the inner toothed rim 24 from the actuating shafts 21 to the user means.

It has in practice been ascertained how the described invention achieves the intended objects and allows the transmission of the motion generated by motion generator means, such as, e.g., an electric motor, to user means such as, e.g. the drum of a winch.

Conveniently, the transmitted motion is reduced by a planetary mechanism. Furthermore, the planetary mechanism is provided with an integrated braking assembly, defined by the worm gearbox assembly, to block the transmission of the motion from the user means to the generator means.

Finally, such integration occurs without significantly affecting the size of the gearbox itself.